- `N = nargin ()`
- `N = nargin (FCN)`

Return the number of input arguments supplied to the current function, or the
declared number of input arguments for function `FCN`.

For functions with variable input arguments, the returned value may be
negative.

See also: `nargout`, `narginchk`, `inputname`.

### References

- https://www.mathworks.com/help/matlab/ref/nargin.html
- https://octave.sourceforge.io/octave/function/nargin.html